The data is chilling: 60% of human infectious diseases are zoonotic, that is, they are found first in an animal, and there are already more than 200 known types of zoonoses, warns the World Health Organization (WHO).

The figure can even rise to 75% for new infectious diseases and, among the pathogens responsible for these diseases, one in six would be a virus, a third a bacteria and another third parasites.

Wildlife species are a major source of microbial diversity and an important reservoir of emerging infectious disease agents,” the World Livestock report already warned in 2013. Changing disease landscape, prepared by FAO.

When, at the end of 2019, COVID-19 began to spread across the Asian continent, all eyes fell on the so-called wet markets of Wuhan, China, and on bats.

To date, the WHO maintains that it is “probable” that an animal served as a host in the transmission of SARS-CoV-2, which confirms the role of these as reservoirs of viruses capable of infecting man. Now, what are the main animals responsible for the transmission of viruses and diseases in recent years?

Bats

With more than 1200 species in the world, bats are the second most specific taxonomic group of mammals after rodents.

These animals, which act as a reservoir for a large number of viruses that affect humans, without becoming ill themselves, have been associated with several zoonotic ailments, related to major diseases in humans and animals, including severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), Ebola and Marburg viruses, and nipah virus (NiV), which appeared in 1998, details the study Infectious Diseases in Bats, published by Jonathan H. Epstein.

Around the world, there are about 1,200 species of bats, animals associated with the spread of SARS and MERS (Shutterstock)

Around the world, there are about 1,200 species of bats, animals associated with the spread of SARS and MERS.

Pigs

Pigs can play a role in intermediate host for influenza viruses and nipah, for example, emerged in the late 1990s in Asia. This animal, sensitive to human viruses, is also is conducive to recombinations.

This is probably what happened during the H1N1 (influenza A) pandemic between 2009 and 2010, initially called “swine flu”. The virus strain would have arisen from a pig carrying both bird flu and human flu.

Dromedary

Also known as Arabian camel, this single-humped animal appears to be a large MERS reservoir host and an animal source of infection in man.

According to WHO data, this viral respiratory disease was first detected in Saudi Arabia in 2012. Since then, cases have been detected in 27 countries, including the United Arab Emirates, Qatar and Egypt.

The dromedaries, characterized by having a single hump, were related to MERS (Shutterstock.com)

The dromedaries, characterized by having a single hump, were related to MERS.

Monkeys

Primates served as intermediate hosts for HIV (starting with the Simian Immunodeficiency Virus, also known as SIV), and researchers believe that the disease initially reached humans through wild chimpanzees living in central Africa.

Although it is estimated that the AIDS epidemic appeared in Kinshasa, today the Democratic Republic of the Congo, about 100 years ago, only in the 1980s, the journal Science announced that a researcher was able to isolate the virus. HIV, which continues to be one of the world’s biggest public health problems, claimed some 33 million lives, according to the WHO.

In addition, the monkeys are also believed to have been able to transmit Ebola. According to investigations, the origin of the outbreak would have been the meat of some infected monkeys of the red Colobus species that the chimpanzees attacked.

One of the scientists who carried out autopsies on the infected chimpanzees contracted the disease. Ebola outbreaks today have a fatality rate that is approximately 50%, warns the WHO.

Mustellids (minks, weasels, otters, and ferrets)

Mustelids are a family of mammals, carnivores, both terrestrial and aquatic, which on several occasions were identified as responsible for viral zoonoses, and in particular those caused by coronavirus.

Among them there are about 60 different species, such as minks, weasels, otters and ferrets, who knew how to become fashionable recently. According to the Spanish Animal Health Research Center (CISA-INIA), mustelids can transmit COVID-19.

In addition, Within this family, the civet was identified as an intermediate host of SARS, which left 774 deaths globally between 2002 and 2003. However, the data is not confirmed yet.

The ferret, belonging to the mustelidae family, was identified as an animal that can transmit viruses (Pixabay)

The ferret, belonging to the mustelidae family, was identified as an animal that can transmit viruses.

Pangolin

Commonly known as a pangolin, the folidot (it owes its name to the fact that it is covered by scales) is an endangered placental mammal and it has 8 species.

When the cases of COVID-19 began to be known, this animal that lives mainly in Asia and Africa was in the sights of Chinese researchers as the “possible intermediate host”, given the proximity of the genetic sequences of SARS-CoV-2 and a coronavirus that infects pangolin. However, this fact is not yet proven, although it is known that this mammal is the natural host of many viruses.

Mosquitos

Although the word “zoonosis” refers to vertebrate animals, insects, such as mosquitoes, can transmit various diseases, such as yellow fever, Zika, chikungunya, West Nile virus, Japanese encephalitis, and Rift Valley fever.

The aedes aegypti species, by case, transmits dengue, a disease prevalent in tropical and subtropical areas, which produces a severe flu-like syndrome and can sometimes lead to a life-threatening condition known as severe dengue. According to the WHO, the incidence of the disease has multiplied by 30 in the last 50 years.

Detail of the Aedes aegypti mosquito, a species that can transmit dengue and yellow fever (EFE / Gustavo Amador / File)

Detail of the Aedes aegypti mosquito, a species that can transmit dengue and yellow fever.

Birds

Spanish flu (1918-1919), Asian flu (1957), Hong Kong flu (1968), H1N1 (in 2009 and 2010), All these viruses responsible for large influenza pandemics had, directly or indirectly, an avian origin.

According to research, two other strains of avian origin, H5N1 (between 2003 and 2011) and H7N9 (since 2013), gave rise to direct infections with infected birds in Asia, or in very rare cases of human-to-human transmission.

Wild birds can be the starting point for such epidemics, and farmed birds very often play a role as “amplifier populations”.

Foxes, as well as dogs, cats and other mammals, can spread rabies (Shutterstock.com)

Foxes, as well as dogs, cats and other mammals, can spread rabies.

Foxes

This animal, like infected dogs, cats, ferrets, and raccoons, can spread rabies to humans. This type of disease (which is different from the one spread by bats) is responsible for the vast majority of the 59,000 deaths annually.

Rodents can be a reservoir for viruses, such as hantavirus (Shutterstock.com)

Rodents can be a reservoir for viruses, such as hantavirus.

Mice and rats

Rodents are also known to be the reservoirs of many viruses, including Lassa hemorrhagic fever, endemic in several West African countries, and hantavirus. In the United States, human hantavirus infections were first identified in the Southwest in 1993.

In recent years, sporadic cases have occurred in several eastern states. Also in the Patagonia of Argentina there was an outbreak at the end of that same decade.

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